This is a tool for estimating federal income tax. It is intended to help you determine how much federal income tax you would owe given the information you provide. Unlike programs for doing your taxes, this tool does very few calculations. The following list shows the calculations that are performed. Beyond these calculations, the tool just uses information you enter, which can be from a previous tax return and adjusted based on your changing situation.
There is also very little checking so you can enter whatever you like and see how it affects your taxes. For example, you can see the effect of selling a stock (capital gains), or whether you have enough deductions to itemize deductions. However, some inputs will be restricted to values based on limits in the tax law. This won"t cause an error, but internally, the value will be replaced with its maximum value. The following list shows the current limits that are imposed.
The tax formula for calculating the federal income tax is also provided to show, at a high level, how the tax is calculated. The value of each item in the tax formula is shown in the "Estimated Tax Calculation" section.
The remainder of this document describes the fields that are computed (blue) and the fields where you can enter data (green). The fields are listed in the same order as they appear in the tool. This is also the same information that is displayed in the tool tips.